Britain's Prime Minister Liz Truss has vowed to reboot her economic programme, but Conservative critics warned the party faces electoral oblivion under her leadership.

With even US President Joe Biden joining in attacks on her libertarian platform, Ms Truss admitted it had been a "wrench" to fire her friend Kwasi Kwarteng as chancellor of the exchequer on Friday.

But writing in the Sun on Sunday newspaper, she said: "We cannot pave the way to a low-tax, high-growth economy without maintaining the confidence of the markets in our commitment to sound money."

That confidence was jeopardised on 23 September when Mr Kwarteng and Ms Truss unveiled a right-wing programme, inspired by 1980s US president Ronald Reagan, of £45 billion in tax cuts financed exclusively by higher debt.

Markets collapsed in response, driving up borrowing costs for millions of British people and the Conservatives' poll ratings have similarly slumped, leading to heavy criticism in the governing party mere weeks after Ms Truss succeeded Boris Johnson.

"I think the game is up, and it's now a question as to how the succession is managed," senior Tory MP Crispin Blunt said on Channel 4.

Ms Truss has been forced into a policy U-turn which cost Mr Kwarteng his job. But she depressed the bond markets even more with a press conference on Friday and the government was nervously awaiting the resumption of trading tomorrow.

Jeremy Hunt was brought in to replace the sacked Kwasi Kwarteng and restore credibility to Downing Street

Bidding to placate investors, Mr Kwarteng's replacement Jeremy Hunt is now warning that taxes may in fact have to rise, and is pressing for spending restraint by his cabinet colleagues even as people endure a cost-of-living crisis.

Mr Hunt today met the prime minister at her country retreat to thrash out a new budget plan which he is due to deliver on 31 October, effectively demolishing the "Trussonomics" programme that brought her to power.

"It's going to be very, very difficult, and I think we have to be honest with people about that," Mr Hunt told the BBC -- prompting a warning from trade unions of concerted strike action if he enforces painful cuts.

Mr Hunt said he was "not taking anything off the table", but also defended Ms Truss.

"She's been willing to do that most difficult of things in politics, and that is to change tack," he said, adding: "The prime minister's in charge."

The Treasury declined to confirm reports that Mr Hunt plans to delay a planned cut to the basic rate of income tax, removing yet another headline measure announced by the new government last month.

Up to 100 letters expressing no confidence in Ms Truss have been submitted by Tory MPs, the Sunday Times and Sunday Express said.

Opponents were said to be coalescing around Ms Truss's defeated leadership rival Rishi Sunak and another one-time rival, Penny Mordaunt, for a possible "unity ticket" to rebuild the stricken Tories.

Defence Secretary Ben Wallace could be another compromise candidate for leader, the Sunday Mirror reported.

Tory MP Robert Halfon, chairman of the Commons Education Committee, did little to quash those rumours during an appearance on Sky News, when he declined to deny that MPs are considering installing a new leader.

"Of course, colleagues are unhappy with what is going on," he said.

"We're all talking to see what can be done about it."

While he stopped short of calling for the prime minister to go just yet, he did launch an extraordinary attack on the government and the guiding philosophy of the mini-budget.

"I worry that, over the past few weeks, the government has looked like libertarian jihadists and treated the whole country as kind of laboratory mice on which to carry out ultra, ultra free-market experiments. And this is not where the country is.

"There's been one horror story after another."

Former culture minister Nadine Dorries, a loyal follower of Boris Johnson, wrote in the Daily Express: "The sad truth is that those scheming to eject the Prime Minister from Downing Street are the same plotters who conspired to get rid of Boris. They will not rest until they have anointed their own chosen leader in power."

Additional reporting: PA